1. Field of the Invention
The present invention relates to a tank flow path structure that is mounted on the upper part of a fuel tank and is for connecting the inside of the fuel tank to the outside.
2. Description of the Related Art
A tank flow path structure is disclosed in JP-A-2002-137641 and JP-A-11-315765, which is constructed in a fuel cutoff valve for ventilating the inside of the fuel tank to the outside. The fuel cutoff valve is mounted on the upper part of the fuel tank, and comprises a casing with a connection conduit connected to the outside (canister), and a float that rises and falls with the increase and decrease of buoyancy according to the fuel fluid level within the casing valve chamber. The fuel cutoff valve ensures ventilation between the fuel tank interior and the outside during fueling and the like, and prevents fuel in the fuel tank from flowing out canister by closing the connection conduit by the float rising due to an increase in buoyancy with a rise in the fuel fluid level of the fuel tank.
In recent years, to handle the varied and large occupation space of vehicles, flattening of fuel tanks has been studied. However, with the fuel cutoff valves of the prior art, from the design condition of the connection conduit ensuring flow volume of a specified level or greater, the flow path area of the connection conduit is made larger and the hole diameter of the connection hole which is the opening of the connection conduit is also made larger. However, with a connection conduit for which the connection conduit area is made larger in this way, the height direction shape of the fuel cutoff valve is also larger, which hinders the flattening of the fuel tank described above. Also, there is a high possibility of fuel leaking from within the fuel tank because the connection hole is larger.